Humure Coffee Washing Station, where coffee from Remera Hill was processed
Humure Coffee Washing Station, where coffee from Remera Hill was processed

July 2023

Newsletter archive

July 5, 2023
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July 5, 2023


AUGUST - response requested!

First things first! As mentioned in the last newsletter, Sam and Peter will be out of town during the first week of August. Subscriptions will bill on the 1st, as usual, but we will fulfill your order either early (July 25) or late (August 8). Please take a sec to record your preference via this form! If we don't hear from you by the 17th, we'll choose :)

Remera Hill

Back for the second year, this month's coffee comes from a group of growers located near Remera Hill that deliver coffee to Baho Coffee's Humure station. Flavor wise, this coffee was absolutely one of our personal favorites over the last year, and we're so excited to have it back! This year's crop underwent a slightly extended low oxygen fermentation which provides us a great opportunity to chat about....


...barely disguised Marxist economic theory! Oh wait - sorry, totally mixed that up with every other newsletter. We're actually going to be doing a little Coffee Processing 101 this month. While I (Peter) am an avid fermenter and the basics of fermentation are somewhat universal, neither of us are experts on this stuff! If you're interested in learning from the pros, we definitely recommend checking out Lucia Solis and her podcast Making Coffee.

Cherry -> espresso

Coffee (specifically coffea arabica) is a shrub native to Ethiopia. It flowers and then forms a fruit that is botanically known as a drupe, which just defines how the ovaries of the flower are transformed into the hard stone part of the fruit, the seed. Plums, cherries, peaches, dates, pistachios, etc. all also form drupes.

Coffee fruits are picked as (hopefully!) ripe cherries. Although it varies widely, a healthy tree will end up producing just a pound of roasted coffee per year, which is around 2000 cherries or about 10 pounds. After picking, various layers of the cherry are removed and/or dried until just the dry seeds remain (at around 10-12% moisture content). These green seeds are what finally goes in the roaster, and later into someone's latte!

Do y'all have any coffee flavored coffee?

Fermentation is a huge part of what makes coffee delicious, and if you're a coffee nerd, you're probably aware that the specialty coffee industry is obsessed with boutique, "innovative" processing techniques. If you can think of any fermentation style or ingredient, it has probably already been added to or used to culture coffee (yeasts, lactobacillus, koji, fruits, spices, infusions, etc). These coffees can taste incredible! Or weird and unbalanced, even boring! There are a lot of variables, and there's also a lot of hype.

To be clear, all coffee is fermented. Even with the quickest processing, it would be hard to completely stop microbiological activity. Fermentation also plays a role in breaking down the layers of the cherry, making separating a roast-able seed much easier. But fermentation also contributes flavor!

Sweetness in coffee

As a baby barista, I was told that coffee gets its sweetness from the sugars in the fruit. And as the fruit dries, sugar is absorbed by the seed. There's truth to this! The sweetness in coffee is related to the sugar in the coffee cherry, but it isn't a direct relationship. The seeds are pretty dense, and are actually drying throughout the coffee processing. Sugar is very water soluble and a lot of it is left behind when the coffee is milled. Green coffee is still ~10% simple and complex sugars, but this is almost entirely caramelized (consumed) in the roaster.

It turns out that the sweetness we taste is due to aromatic compounds! There are lots, and it's a little over my head, but compounds like esters, furaneol, and ethyl-somethings trick your brain into "tasting" sweetness even in the absence of sugar. You can test this by tasting coffee with your nose pinched. It won't totally shut off your ability to perceive aromatics, but it will absolutely reduce sweetness (and other flavors). Diluted sugar water won't be affected in the same way.

To wrap it all up, lots of the aromatic compounds that help us perceive flavor in brewed coffee are a result of the fermentation! So, coffees that have a higher sugar content as cherries have more gas in the fermentation tank. And controlling the fermentation, whether subtly (like in the case of this month's coffee) or more heavily handed (with inoculation or additives), will effect the profile of aromatics and the perceived flavor of the coffee. The specifics are very complex and contingent, and it's the job of people like Lucia to help producers understand and improve their practices and investments in fermentation.

Low O2, anaerobic, carbonic, etc.

This year's Remera Hill was fermented in a low O2 environment. After sorting out defects, the cherries were placed in sealed tanks for 40 hours, with the CO2 from fermentation displacing other gases in the tank over time. This gave native bacteria and yeasts that prefer a low oxygen environment a head start on competing microorganisms. Specifically, this environment will encourage naturally occurring yeasts and lactobacillus to multiply, with an incredibly complex array of simultaneous fermentation and enzymatic processes at play. In the case of Lactobacillus, many strains are heterofermentive, meaning they can convert sugar into either lactic acid (like in kefir, sauerkraut, etc.) or into ethanol and CO2 like yeast. The early phase of a fermentation is crucial to establishing the dominant strains and with them, the flavor characteristics of the final ferment.

Low O2, often called anaerobic or semi-carbonic is an accurate description for a process that is used in coffee a lot. Also used in wines and other ferments (maybe you've heard of carbonic maceration?), it generally produces fun, fruit-forward, zippy ferments! This is true for wine, ciders and coffee, and it can be really fun to draw connections and comparisons across fermentation traditions!

Ok folks, see ya next time!